EOS scanner provides higher level of imaging with less radiation
By John Thometz, MD
Children's Hospital of Wisconsin is one of the first two pediatric hospitals in the country to obtain EOS X-ray imaging technology. This technology is a radical improvement over standard radiographic imaging of the spine and lower extremities in multiple ways. The EOS is able to obtain a standard PA and lateral scoliosis film with 1/10 the amount of radiographic exposure of standard low-dose films. The EOS is able to obtain 3-D visualization of the spine with 1/1,000 the dose of a CT scanner. In addition to providing a standard 2-D film, EOS also allows for 3-D reconstruction of individual bone position, rotation and orientation. Not only does the EOS capture a simultaneous PA and lateral radiograph of the spine, it also has the capability of whole body radiographs in the standing position. This comprehensive view of spine and joint alignment allows for a more accurate assessment of deformities.
It is well known that in children with scoliotic deformity, there is not only a progressive lateral deviation of the spine but this is associated with a progressive rotational deformity of the vertebral bodies themselves. The spine progressively rotates, creating the rib hump – over time, the ribs themselves become more deformed. The deformity is difficult to assess with the use of 2-D films. However, this rotational prominence is the problem most adolescents are concerned with. Many treatments have been devised to stabilize the curvature or reverse this cosmetic deformity. Until now, there have been very poor methods for accurately assessing the results of treatment. EOS provides a better handle on the correction of the deformity.
The EOS is based on a patented technology developed in France that received the Nobel Prize in physics. This technology eliminates the vertical distortion that is common with traditional radiographs. It enables long-length digital imaging without the need for "digital stitching," which can lead to inaccuracy in assessment of the spine or lower extremities.
Since the EOS has been in use at Children's Hospital, not only has the radiographic dose reduced drastically, the clarity of the radiographs also has improved greatly. (See Images 1 and 2.) The bony detail that can be seen, especially in the lumbar spine and pelvis, is much better than it was before. This allows more accurate assessment of bony pathology and bony landmarks, which are used to assess skeletal maturity. It is particularly exciting to note that this allows for assessment of 3-D skeletal reconstruction. (See Image 3.)
Traditionally, treatment (either bracing or surgical intervention) is defined by 2-D X-ray assessing a 3-D deformity. The use of the EOS now allows accurate calculation of the change in the position of the individual bones and their displacements and rotational deformities, and this is critical in assessing the results of treatment interventions. With EOS, 3-D bone modeling is possible, which defines the relative positions of each vertebra, and therefore enables better preoperative surgical planning and better postoperative assessment of results. (See Images 4 and 5.)
Scanning technique
When the patient stands inside the EOS device (see Image 6), simultaneous AP and lateral X-ray images are acquired by a vertical scan from head to toe. The results are available within seconds and the fact that it is possible to take a simultaneous AP and lateral film from head to toe allows for much improved assessment of global posture and improved assessment of limb length discrepancies, angular deformities or other pathology in the lower extremities. Three-D images of osseous deformities, which in the past could only be obtained from a CT scan, now can be assessed with the EOS. More than 100 clinically relevant angle and leg length measurements can be calculated automatically with this technology. This allows for better preoperative planning with drastically lower radiographic exposure. EOS provides a more precise measurement in children who have a leg length discrepancy since it eliminates the distortions seen with a standard radiograph.
Radiographic exposure reduction
At Children's Hospital of Wisconsin, we have had a long-standing commitment to minimize radiographic exposure during scoliosis imaging. Young children with scoliosis who need to be followed through the years require multiple radiographs and, over time, the total radiograph exposure can increase the risk for breast carcinoma, thyroid carcinoma or other tumors. Our center has been a leader in use of surface topography for following children with mild curvatures to avoid the use of radiographs. The use of surface topography has allowed us to avoid the use of thousands of radiographs in the assessment of our young patients with spinal deformity and in some cases has allowed patients to avoid 16 or 17 spinal radiographs. Currently, we are involved with new and improved technology for surface topography.
The EOS device is a fantastic advance for children with scoliotic and lower limb deformities. It also will allow us to conduct cutting-edge research to describe the results in conservative and surgical intervention for scoliotic patients. With the dramatic reduction of radiographic exposure, improvement in the quality of the radiographs and ability to assess the deformity in 3-D, the EOS enables a dramatic improvement in the quality of the care provided.
John Thometz, MD, is medical director of Orthopedic Surgery at Children's Hospital of Wisconsin, professor and chief of Pediatric Orthopaedics at The Medical College of Wisconsin and a member of Children's Specialty Group.
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